Form for concrete conduit construction.



F; s.- VGRAEF.

FORM FOR OONORETE GONDUIT CONSTRUCTION.

\ APPLICATION FILED ssflnzz, 1909.

1n: uanms PETERS cm, WASHINDTEN, a. c.

FRANCIS SAVIER GRAEF, OF NEW YORK, N. Y.

FORM FOR CONCRETE CONDUIT CONSTRUCTION.

Specification of Letters Patent.

Patented July 5, 1910.

Application filed September 22, 1909. Serial No. 519,063.

To all whom it may concern.

Be it known that I, FRANCIS SAVIER GRAEF, a citizen of the United States, residing in the city, county, and State of New York, have invented new and useful Improvements in Forms for Concrete Conduit Construction, of which the following is a specification.

My invention relates to improvements in interior forms for molding tubular constructions of cement concrete, or similar plastic form in readiness for the molding process.-

Fig. 1, indicates the modification in the bottom of the form when collapsed into position for withdrawing it from the molded concrete. Fig. 2, is an elevation of a portion of the longitudinal side of the form.- Fig. 8, is a sectional plan on the line X, X, in Fig. 1, showing the bottom of the set-up form. Fig. 4, is a perspective of the form reduced.

The basis of the structure of the form con sists in elastic ribs (preferably of a good quality of spring steel) indicated by A, in the drawings. These ribs are formed to coincide in contour with the shape designed for the interior of the conduit, transversely through the same. Upon these transverse ribs are fastened parallel longitudinal strips, similar to B, in the drawings; these strlps being placed at intervals around the ribs in circumferential series completing the skeleton of the form (as shown in the upper portion of Fig. 1) over which is stretched a covering of sheet metal, shown in part at C in the drawing, constituting the outer surface of the form, upon and around which the concrete is molded, as shown in part by the portion indicated by D in the drawings.

The ribs, A, do not consist of complete, unbroken bands, but their disconnected ends normally nearly meet to comprise a complete circuit, bringing the bottom edges of the form together as shown at O, in Fig. 1. In this view it will be seen that the ends of the rib are respectively secured to the longitudinal strips B, at the margins of the skeleton form, these end strips having their marginal edges Z), beveled inward as indicated, in such wise that the opening between these strips widens inward. While this is the normal position of the disengaged form, the flexibility of the structural ribs, A, makes it practicable to expand it very considerably, and to allow of the insertion of a spreader, E, which comprises in its outer contour the are necessary to the completion of a circuit of larger dimensions than that of the form in its normal condition, and fixes conjointly with the form proper the dimensions and contour of the interior of a tube molded therewith.

The spreader, E, is held in position by the turn-buttons, F F, shown connected. to the edge strips Fig. 1, and haschamfered edges fitted to the edges of and adapted to easy removal from the mold proper. These edges are indicated by G G, and the spreader is therefore wider 011 its inner than on its outer surface.

After the concrete has hardened the spreader is removed by releasing the buttons,

. F F, and lifting it out of its position in the form. The form may then be collapsed into its normal position as indicated in Fig. 1, in which the space between the outer covering, C C, of the portion of the form shown, and the inner part of the portion of concrete, D D, indicates the consequent shrinkage in the circumference of the form whereby its easy removal from the construction is providedfor.

In Fig. 8 the bottom of the form is shown. The spreader, 'E, is extended out beyond the end of the form to facilitate the handling of it. The turn-buttons are shown locked at F F, and unlocked at F F, Fig. 3.

While conduit construction is illustrated only in circular form in the drawings, it is obvious that my invention is likewise adapt- ;ble to oval, elliptical and other curvilinear orms.

To facilitate the setting up of the forms and to insure a perfect bottom (which is reached with difliculty, and hence not easily molded, by use of thetamping iron) it is desirable to construct a bed of concrete (as indicated between the dotted lines H H, in

r 7 claim:

Fig. 1,) and this to harden before s etting up the form. 7

7 Having thus described my invention, I

1. An expansible core-form for molding tubularstructures, consisting ofa series of transverse expansible flexible ribs having the proper contour,

rated longitudinal strips secured to said a' series of sepa- "fleXible ribs and having end strips provided :withinward beveled edges, 7 a bevel-edge "removable spreader widening inward to correspond with the end strips, fastening turn- ;buttons attached to the end strips, and a sheet'metal covering on vthe longitudinal constituting the outside of the form.

. 2. In anjexpansible core-form i'or molding tubular structures, the combination with a longitudinal series of circumferential automatically' contractlng elastic contour r1bs having; separate ends, of a serles of par- I U allel longitudinal strips separated by intervals, and permanently secured to ,said ribs,

marginal strips securedto the rib ends, an inward-movable spreader member, and releasing fastenings.

l 3 In anexpansible core form for m01ding concrete structures, the combination with 21 circumferential series. of parallel longitudinal strips separated fromeach other by intervals,of a longitudlnal serles of automatically contracting elastic contour ribs having unconnected ends and permanently secured to the inner surfaces of said strips,

marginal strips secured tothe rib ends, an

outer covering of thin sheet metal, an inward movable spreading member, and releasing fastenings.

4.7An expansible core-form for molding concrete, consisting of a longitudinal series of automatically contractin elastic contour ribs having unconnected an separated ends,

a circumferential series of parallel longitudinalstrips separated from each other by intervals and secured, to the outside of said ing s reader, and means for securing the 'sprea er between said edge'str ps.

6. In an expansible core-form for molding concrete, an automatically contractin skeleton form consisting of a longitudina series of elastlc'contour r1bs having unconnected ends, a clrcumferential serles of longitudinal strips fastened to said ribs to form a unitary structure, marginal strips fastened to the 'rib' ends, a removable longitudinal spreader adapted to be seated between said marginal strips, and releasing fastenings in connection therewith.

v FRANCIS SAVIER GRAEF. Witnesses:

INDA G. GRAEF, ADA GAscoYNE GRAEF. 

